I recently bought a few bottles of unopened transfer box fluid for my LR3.

I have no way of telling how old the fluid is, but it seems to have done something over time to reduce the volume of air inside the bottle, either reacted with or absorbed a gas in the air.

I don't know if transfer box fluid tends to absorb moisture, but would be surprised if there is really that much moisture in air.

So what's causing this behavior, and does it affect the meaningfully affect the efficacy of the fluid?

Special Transfer Box Oil

  • 1
    Are you sure it used to have more air in it? They may have been bottled like that to allow them to be sent in an aeroplane (airplane).
    – HandyHowie
    Commented Mar 13, 2018 at 8:50
  • @HandyHowie I don't think they'd make assumptions about whether it's to be air-freighted. All pictures of such bottles on online stores look normal to me. Here's an example.
    – Zaid
    Commented Mar 13, 2018 at 9:03

1 Answer 1


This is usually because the ambient air pressure when the bottle was filled is less than the current ambient air pressure where you are.

The other possibilty is that a temperature reduction will also have the same effect.

Usually a combination of both together though.

This was a classic experiment in physics at school by boiling water then sealing the container and allowing it to cool...

  • Plausible from a physics perspective, but my climate is far hotter than the UK's, which I assume is where the fluid is sourced from (I can confirm this when I get back home).
    – Zaid
    Commented Mar 13, 2018 at 9:10
  • So think about the air pressure, which was the first part of the answer.
    – Solar Mike
    Commented Mar 13, 2018 at 10:34

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